Focus is on Trackers to Achieve Lowest LCOE with Bifacial & Monofacial Modules

Globally the market is already rooting for trackers and the market is predicted to achieve 48 GW by 2027. Considering the increase in installation and material cost trackers seems the more suitable option for Solar plants in India. With proposed duties on modules, increasing cost of labour and Trackers will help developer achieve low capex cost as the number of pieces will go down. 

Solar Energy Research Institute of Singapore has established that Single-axis trackers offer the lowest LCOE in 90% of the world. Monofacial single-axis tracker plants achieve the second lowest LCOE.

Usually single-axis trackers add 25% to that bifacial gain, compared with fixed systems with Monofacial panels.

With module and tracker improvements, solar tracker prices are declining on a dollar cost per watt. Developers can get huge benefits from solar trackers and module innovations, Soltec continues to invest in research and development to adapt with new module innovations. Focus is on Tracking Algorithms and Structure design to gain more from less.  

Soltec’s Teamtrack Backtracking
The backtracking algorithm uses NREL sun-position data versus programmed constants of local irregularities to execute energy optimized backtracking position control, avoiding inter-row shading in the early and late-day hours due to uneven terrain influences and achieving yield-gain. TUV Rheinland has verified that the algorithm meets the specifications by remodeling the increased energy gain and analyzing the modeling results.

In order to evaluate the robustness of the algorithm at different locations with different environments TUV Rheinland performed the verification for 27 defined scenarios and confirms that Soltec’s TeamTrack algorithm leads to higher annual yield gains in the range between 3.6% and 7.5% in comparison to a standard tracking algorithm (s. Figure 1).

Soltec’s Layout Engineering and Structure Design
Soltec layout design and structure innovations ensure maximum energy gains from the PV plant. Emphasis is on getting the most optimal pitch, design adaptations to avoid shadows and keeping the modules cooler for maximum efficiency.

Pitch and GCR
Pitch is a determining factor in bifacial module generation.

Increased distance between trackers implies more hours of tracking and, therefore, increased module front side generation. In other words, decreased generation resulting from tracker deviation during backtracking is lower. This is true for projects equipped with both bifacial modules and Monofacial modules. 

Maximum tracker angle is another key factor. For the same GCR, trackers with a larger tracking angle can operate longer in tracking mode (directly facing the Sun), thus generating more power by direct irradiation. When solar elevation exceeds the limit angle, tracking stops and energy is lost.

Increased Rear Radiation with Height
Bifacial module height has a direct impact on power generation because as module distance from the ground increases, bifacial module rear side irradiation does too. Module distance from the ground facilitates diffuse radiation penetration and increased view factor. Optimal bifacial module height ranges between 2 to 2.5 meters 

Similarly to Monofacial modules, shading has a negative impact on bifacial module performance. Some analysts suggest that module mounting system shading could result in a rear irradiation loss of up to 20%. 

In the case of standard 1P solar trackers, the torque tube is a significant module shading source. A number of analyses point out the fact that projected 1P tracker torque tube shading projection varies along the module depending on the time of the day, potentially reaching an irradiation decrease of up to 15% with a distinctive peak. Specific interference location does not only favor reduced rear radiation, but also increases mismatch losses and may contribute to overheating of some cells, and as a result, a premature module degradation. 

Influence of Height and Pitch -
Cooling The electrical conversion efficiency of a PV cell decreases as temperature increases, meaning the power generation of a module, both bifacial and Monofacial, increases as module cooling improves. The downside on bifacial modules is that they generate more heat due to rear side irradiation capture, meaning they tend to work at higher temperatures and, therefore, need additional cooling. 

According to temperature distribution along the tracker, it decreases as distance from the ground increases. This trend applies to both 1Pand 2P tracker, meaning the average temperature of the lower module in a 2P tracker is similar to that of the 1P tracker module. As for the upper module, temperature values are lower. Measurements show that the average difference of 6 degrees Celsius translates into a power gain for the entire plant of about 1.2%. 

Enhanced cooling is caused by three factors. On the one hand, 2P tracker modules are further away from the ground, hence favoring air flow circulation under the tracker. On the other hand, aisles are twice as wide, hence favoring improved air inlet between rows. Lastly, SF7 Bifacial tracker design allows cool air to flow through the gap in the central part of the structure. 

According to Lujia Xu, a postdoc researcher at Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) “Lowering module temperature by around three degrees Celsius could bring about the same improvement to levelized cost of electricity (LCOE) at project level as a 1% increase in module efficiency. Findings also show that reducing operating temperature can also greatly increase a module’s lifetime”.

Analyzing the module cooling effect in a market like India where summer temperature goes to 50 degrees in many parts can definitely help developers in gaining the lowest LCOE with best tracking system design and module combination.

- Karishma Dagar, Regional General Manager, Soltec